1. Field of Invention
This invention relates generally to machine tools, and more particularly to a machine tool having a machining spindle, a device for inserting an auxiliary unit into the machining spindle, a tool magazine for providing a multitude of tools and a tool changer having at least one tool gripper for holding tools for the machining spindle for the transportation of tools between the tool magazine and the machining spindle.
2. Discussion of Related Art
In known machine tools of the above mentioned type, for example, a high speed spindle or a polishing head insertable into the machining spindle, if necessary, are used as the auxiliary unit. Thus the speed range for certain machining operations can be increased and the application range of the machine tool can be widened. For high speed spindles or other auxiliary units, however, generally tool holding fixtures different from those used for the machining spindle are required. In conventional machine tools the tool exchange at the auxiliary units is therefore often effected manually or by separate changing devices. This is either time consuming or requires increased expenses with respect to construction and control.
It is a primary purpose of the invention to provide a machine tool of the above mentioned type enabling a fully automated supply of the respectively required tools to the machining spindle as well as the auxiliary unit to be inserted into the machining spindle in a simple and fast manner.
The most important advantage of the machine tool according to the invention is that not only different tools for the machining spindle but also a plurality of tools for an auxiliary unit inserted into the machining spindle can be provided for machining and may be automatically exchanged by a common tool changer. For the automatic exchange of the tools in the auxiliary unit no expensive additional driving and control elements are required. Thus a fully automated complete machining may be carried out without manual operations.
The tool changer comprises a quadruple gripper arrangement including two diametrically opposed tool grippers for holding tools for the machining spindle and two additional tool grippers respectively displaced by 90xc2x0 with respect to these for holding tools for the auxiliary unit. By simply rotating the quadruple gripper arrangement by 90xc2x0 the tool changer can thus be used as a double gripper for supplying tools to the machining spindle or as a double gripper for supplying tools to the auxiliary unit. By the respectively opposed pairs of grippers a previously used tool on the machining spindle can be replaced by a new tool taken out of the tool magazine beforehand by turning the gripper arrangement by 180xc2x0. Thus a fast tool exchange, including minimal control requirements, is enabled at the machining spindle as well as at the auxiliary unit inserted into the machining spindle.
The auxiliary unit may, for example, be a high speed spindle, a polishing head or any other assembly device by which the range of applications of the machine tool may be widened.
The tools are generally held in special tool holding fixtures by corresponding clamping cones. Since the tool holding fixtures for the machining spindle are, as a rule, larger than those for the tools of the auxiliary unit, the corresponding tool grippers for the respective tool holding fixtures are also of a different sizes.
In a constructively simple embodiment the tool gripper is disposed on a support horizontally movable on a frame of the tool magazine by means of a linear drive and can be rotated about a vertical axis by means of a motor. The horizontal movement of the support and the rotation of the tool gripper may be effected via electrical, hydraulic or pneumatic actuator drives.